Argentina has stepped up a diplomatic offensive over the sovereignty of the Falkland Islands with its foreign minister taking a direct swipe at David Cameron.

H ector Timerman accused the Prime Minister of "forgetting the peace message ... that Christmas should inspire" by stressing in his festive message the UK's commitment to defend the disputed overseas territory.

It comes days after Argentina's president Cristina Fernandez de Kirchner set up a new taskforce to "better defend" the interests of what Buenos Aires calls Las Malvinas.

Mr Cameron used a Christmas message to condemn a "shameful" attempt to deter oil exploration in Falklands waters through a new law imposing heavy jail sentences and fines.

A 2013 referendum in which islanders voted by 1,513 to three in favour of remaining British "could not have sent a clearer message", he said, adding that Britain would " always be ready to defend the Falkland Islands".

Mr Timerman dismissed the referendum as a "violation of UN resolutions" and said London's refusal to negotiate on the issue "is compelling evidence that ... the lion roars but does not inspire fear any more".

Britain had "no moral authority , being the country that has most often ignored United Nations decisions, especially when it comes to bringing colonialism to an end", he wrote in an article published by the Argentine embassy in London.

He claimed the recognition by all African countries as well as those of Latin America and the Caribbean of "Argentina's lawful rights".

"The verbal and military threats of the colonial power will continue to be met with Argentina's demand for respect for international law and for UN resolution," he said.

In a reference to Mr Cameron's failure to secure a Commons majority for military strikes against Syria, he added: " As a corollary to a year in which the British Government issued threats to several independent countries, to such an extent that the British Parliament itself had to reject its attempts to launch military actions in the Middle East, the British Government devoted a paragraph of its Christmas address to the military defence of the Malvinas Islands, forgetting - if the British Government was ever able to appreciate it - the peace message that Christmas should inspire."